Blow molded hollow articles with internal features are generally made by a conventional blow molding process using molds with fixed protrusions. The disadvantage of this approach is that the surface of the molded part has open features that have an aesthetically unpleasant appearance. In addition, a substantially planar surface is not available for bonding a covering when open features are located on the first or the second surface of a hollow part.
Blow molded hollow articles with internal ribs are known, and can be made using conventional, blow molding processes. Such techniques are employed in the manufacture of hollow load bearing structures such as carpeted load floors used in automobiles. In a known process, a carpeted load floor is formed by placing a carpet in the mold, and then inflating a parison onto one or more blades to form a hollow article with at least one internal fused rib, and a bonded carpet on one side and along edges.
While the use of internal ribs provides some resistance to part deflection, improvements are required to make a lighter weight blow molded hollow article with an internal structure that has a lower cost, higher stiffness and thinner section for a given mass than a part made by a conventional blow molding process.